Defects existing in walls or surfaces of mechanical systems and structures can result in system failures and in certain circumstances can produce catastrophic effects. Consequently, in situations where mechanical integrity is of prime importance it is desirable to be able to nondestructively inspect surfaces or walls of important structures and to perform preventative maintenance or reduce operational loads or otherwise reduce the potential hazards of failure before such failures occur.
Inspection of specific walls and surfaces may be difficult as a consequence of surface inaccessibility or resulting from the location of the surface within a hazardous environment such as within the containment area of a nuclear reactor. In these situations it is necessary to provide for nondestructive inspection from a remote location and to provide information indicative of both the presence and location of defects.
An acoustic waveguide assembly used for predicting the failure of structured members under stress is disclosed in U.S. Pat. No. 4,352,038.
U.S. Pat. No. 4,308,751 discloses a method for nondestructive testing of rock anchors embedded in stone. The exposed end of the anchor is excited with a source of elastic waves and reflected waves analyzed to assess the integrity of the anchor and its load bearing capabilities.
Another nondestructive inspection process is disclosed in U.S. Pat. No. 3,924,456 in which a workpiece is subjected to stress, and stress waves are observed employing a stress wave sensor to determine the presence of any cracks or defects.
None of the methods previously disclosed are adapted for inspection of a wall or workpiece surface, where the surface to be inspected may be physically inaccessible, or located in a remote location. Furthermore, none of the art disclosed provides simultaneous information indicative of both the presence and location of a defect in a workpiece surface.